1. Field of the Invention:
This invention relates to a cooling system of an internal combustion engine and, more particularly, an improvement in the control of said control system.
2. Description of the Prior Art:
In most conventional cooling systems of internal combustion engines, there is incorporated a by-pass circuit which allows for a circulating flow of a part of cooling water to by-pass a radiator in order to improve the warming-up performance of the engine. Furthermore, it is also practiced to lead the by-pass circuit through an intake manifold to heat up the intake manifold more rapidly during the warming up period of the engine so that the ignition of fuel air mixture is improved. In operation, when a larger amount of cooling water is passed through the by-pass circuit, a better warming up performance of the engine is obtained, while in this case, the engine shows a tendency to be overheated in the normal operation after the warming up. Furthermore, in the case of the structure where the intake manifold is heated up by the by-pass circuit, there is a problem in that the engine performance lowers in high speed operation. Thus, in view of these drawbacks, a limit has been imposed upon the amount of flow through the by-pass circuit.